TABLE A-3. Feasibly irrigable acreage by county and subbasin by 2000, high level 



of development. 



CONVERSIONS: 1 acre = .405 ha 



NOTE: The number of irrigable acres for the low and intermediate development levels are one-third 

 and two-thirds, respectively, of the numbers given here. This table should not be considered an exhaustive 

 listing of all feasibly irrigable acreage in the Yellowstone Basin: it includes only the acreage identified 

 as feasibly irrigable according to the geographic and economic constraints explained elsewhere in this report. 



MUNICIPAL WATER USE 



The basin's projected population increase and associated municipal water 

 use depletion for each level of development are shown in table A-5. Even the 

 13 hm 3 /y (10,620 af/y) depletion increase by 2000 shown for the highest develop- 

 ment level is not significant compared to the projected depletion increases for 

 irrigation or coal development. Nor is any problem anticipated in the availability 

 of water to satisfy this increase in municipal use. 



WATER AVAILABILITY FOR CONSUMPTIVE USE 



The average annual yield of the Yellowstone River Basin at Sidney, Montana, 

 at the 1970 level of development, is 10,850 hm 3 (8.8 million af). As shown 

 in table A-6, the additional annual depletions required for the high projected 

 level of development total about 999 hm 3 (812,000 acre-feet). Comparison of 

 these two numbers might lead to the conclusion that there is ample water for 

 such development, and more. That conclusion would be erroneous, however, 

 because of the extreme variation of Yellowstone Basin streamflows from year 

 to year, from month to month, and from place to place. At certain places and 

 at certain times the water supply will be adequate in the foreseeable future. 

 But in some of the tributaries and during low-flow times of many years, water 

 availability problems, even under the low level of development, will be very real 

 and sometimes very serious. 



85 



